Examples of starch-based biodegradable molded objects include trays, cups, corner pads, etc. One method of manufacturing this kind of starch-based biodegradable molded object is the external heating method, in which the materials are placed into a mold previously heated to a predetermined temperature, and molding is performed using heat conductivity.
However, with methods of this kind, slow molding leads to low productivity, and unevenness in the temperature of the mold causes uneven baking, thus making it impossible to obtain a uniform consistency.
For this reason, in another method, alternating current is supplied to a metal mold, and internal heating is induced in the materials in the mold by electromagnetic wave heating, such as resistance heating or dielectric heating, thereby baking and molding the materials. In this case, the metal mold is divided into two mold halves, which are insulated from each other by an insulating material provided therebetween, and an alternating current electrode is connected to each mold half. Then alternating current is applied to the metal mold through these electrodes, and the materials in the mold are baked and molded by resistance heating or dielectric heating.
However, with the foregoing method using resistance heating or dielectric heating, during molding, liquid contained in the materials evaporates, producing a large amount of vapor, which condenses, causing insulation breakdown, and thus resistance heating or dielectric heating does not go well.